Novak Djokovic made a dazzling start to his Australian Open defence Tuesday as his close rival Andy Murray struggled and home hope Samantha Stosur became the first big name to fall.

World number one Novak Djokovic during the 2012 Australian Open match against Italy's Paolo Lorenzi on January 17. Djokovic powered past Lorenzi 6-2, 6-0, 6-0

World number one Djokovic powered past Italian Paolo Lorenzi 6-2, 6-0, 6-0, in a victory so comprehensive he even won a point with an audacious trick shot between his legs.

By contrast Murray, runner-up to
the Serb last year, was embarrassed by a near-identical party-piece from
Ryan Harrison before subduing the American 4-6, 6-3, 6-4, 6-2.

But Australia's
US Open champion Stosur became a major casualty as she froze in front
of her home fans, allowing Romania's Sorana Cirstea to record a famous
straight-sets win.

Wimbledon champion Petra Kvitova and glamorous Russian Maria Sharapova, the 2008 Open winner, both started strongly and David Ferrer and Milos Raonic progressed safely in the men's draw.

However, Djokovic looked the pick
of the men's players as the Wimbledon and US Open champion launched his
pursuit of a third straight grand slam title in style, exemplified by
his crowd-pleasing trick shot.

Leading 3-0 in the third and
standing on the baseline, Djokovic turned his back to the court and
clipped a shot between his legs to the flummoxed Lorenzi, who
embarrassingly netted.

It was a sign of overflowing confidence in the Serb, who won 10 of 11
finals and went 70-6 last year -- despite being derailed by injuries
after the US Open -- in a season described by some as the best in tennis
history.

"I just have more confidence that
I'm playing on right now. I just believe that I can win, especially
against the biggest rivals in the major events," Djokovic said.

Later, fourth seed Murray, seeking
Britain's first grand slam title since 1936, became the first top-four
man to concede a set and was occasionally troubled by minor injuries in
his match against Harrison.

Stosur, who has only won one match in three tournaments this year,
all in Australia, put in an error-strewn performance as she became the
latest women's grand slam champion to fail in her very next major.

"There's not any other word for it but a total disappointment," she said.

"It's not through lack of trying or not wanting it or anything like
that. I mean, you can't pick the times that you want to play well,"
Stosur added.

"Of course, I wanted to do very well here. You want it to come right
now. I'm thankful that everyone was behind me. I'm sure they will stay
behind me.

"That's sport. Unfortunately you can't pick and choose when it's all going to happen for you."

Meanwhile, second seed Kvitova and Sharapova, the world number four, also made convincing starts at sun-drenched Melbourne Park.

Dulko had no answer to the power of Sharapova's ground strokes, her
forehand particularly damaging throughout the 58-minute encounter.
Sharapova smashed 14 winners past Dulko and forced the Argentine into 22
errors over the two sets.

"I knew I had a tough opponent today," a delighted Sharapova said
afterwards. "I focused on every point and took her time away -- she's a
player who loves time on the ball."

The Russian fourth seed also
showed no signs of a left ankle injury that forced her to withdraw from
the Brisbane International two weeks ago.

Estonia's Kaia Kanepi, who won the Brisbane tournament, beat Sweden's Johanna Larsson 6-2, 6-4 to reach the second round.

Japan's Kei Nishikori also came
through in three sets against Stephane Robert of France and
bullet-serving Canadian Milos Raonic, a winner this month in Chennai,
eclipsed Italy's Filippo Volandri for the loss of just six games.